This invention relates generally to stud fasteners, and, more particularly, to a stud fastening assembly secured to a workpiece by a serrated ring.
A typical example of a stud fastening assembly of this kind is illustrated in Japanese Patent Publication No. 43389/72. As shown in FIGS. 7, 8(a) and 8(b), a stud fastening assembly 10 includes a main body or stud 11 provided with male threads 12 and 13. The main body is threadably inserted into a machined hole 15 of a workpiece 16 and further threadably engaged with an internal thread 17. The main body 11 is provided with a longitudinal serration 14 located between the innermost incomplete screw threads 12a and 13a of external threads 12 and 13.
A fastening ring 18 is provided with an outer serration 19 and an inner serration 20. The inner serration 20 is slidably engaged with the longitudinal serration 14 of the main body 11.
The outer diameter of the external threads 12 and 13 of the main body 11 are larger than the inner diameter of the inner serration 20 of the fastening ring 18. Even if a relative axial movement with respect to the main body 11 is applied to the fastening ring 18, this axial movement is limited under an engagement with either of the incomplete screw threads 12a and 13a. Therefore, the fastening ring 18 forms an engagement member which is integral with the main body, forming a stud fastening assembly.
When the main body 11 of the bolt is threadably inserted to the desired depth in a workpiece 16, an axial force is applied to the uppermost part of the fastening ring 18 and the outer serration 19 is set in a hole 15a, which is slightly smaller than the serration's outer diameter. Material of the workpiece positioned between the individual outer serrations 19 may apply a resistance force against a rotational movement of the fastening ring. Since a relative engagement between the inner serration 20 of the fastening ring 13 and the outer serration 14 of the main body 11 prohibits a rotational movement of the main body 11, no helical movement of the main body 11 is produced, causing the stud fastening assembly to be kept at its close integral engagement with the workpiece 16.
The fastening ring 18 for the stud fastening assembly has an integral form carrying both the outer serration 19 and the inner serration 20, and its axial thickness is larger than its radial thickness. This causes its press machining and plastic work to be difficult, requiring either a cutting work or a sintering formation of powder metal ceramics to be performed. However, such a machining process has a low productivity, and a reduction in cost is difficult.